Sugarcane is a member of the grass family and is valued chiefly for the juices (specially sucrose) that can be extracted from its stems. The raw sugar that is produced from these juices is later refined into white granular sugar.
Sugarcane, which is the raw material for the production of sugar, is a perennial crop. One planting of sugarcane generally results in three to six annual harvests before replanting is necessary. The very first harvest after the planting is called “Plant Cane,” while the subsequent harvests before the next replanting are called “Stubble” or “Ratoon.” The first stubble or ratoon is the first harvest following the plant cane harvest, the second stubble or ratoon is the second harvest following the-plant cane harvest, and so on.
As a sugarcane plant matures throughout the growing season, the amount of total sucrose in the cane increases. Most of this sucrose production occurs when the plant has fully matured and begins to ripen. However, the percentage of sucrose content (or quality of cane juice) mainly depends on various factors such as the sugarcane variety (also referred to as cultivar), the maturity of the sugarcane (the age of the sugarcane from the date of planting in the case of plant cane or from the date of the last harvest in the case of ratoon), weather conditions, diseases, harvesting conditions, delays between cutting and crushing, and the amount of trash in the sugarcane during crushing. Trash can be defined as the amount or quantity of leaves, tops, dead stalks, roots, soil, etc., delivered to the crusher along with the sugarcane. Hence, the accumulation of total sucrose within the sugarcane is a function of its sucrose percentage and vegetative growth. Recovery is a measure of this sucrose percentage.
A typical sugar processor buys sugarcane from various farmers, and these farmers usually have contracts with the sugar processors. Each sugar processor knows the planting date of each crop of the different farmers and the varieties of the sugarcane. The long-term viability of the sugar industry depends upon finding ways to produce sugar more economically through production management decisions that reduce production costs or increase return. Harvest scheduling, which includes decisions about when to harvest which variety (or cultivar) at what age of the sugarcane, is one practice that has a direct impact on the net farm return. The net farm return may be defined as the total sugar (usually by weight) obtained from a given planting.
In one embodiment of the present invention, a methodology is developed for the estimation of sugar recovery (e.g., percentage of sucrose in the sugarcane). This estimation can be used to assist in daily harvest scheduling at the individual farm level. One objective of this methodology is to capture the dynamic effects of sucrose accumulation (which depends on variety, age, weather condition, etc.) during growing and harvesting seasons and to utilize this information, such as in a mathematical program modeling framework, to determine when specific sugarcane fields should be harvested so as to maximize total farm net returns.
As individual sugarcane varieties (or cultivars) have distinct sucrose maturation curves, which may vary up or down from year to year depending upon weather conditions and other factors, the estimated sugar content of individual fields can be incorporated into harvest scheduling that includes an optimal order for harvest of all fields so as to maximize the total sugar produced (or the total net return received).
Several studies have attempted to develop models for estimating the percentage of sucrose in sugarcane. Whan, et al., in “Scheduling Sugar Cane Plant and Ratoon Crops and a Fallow—a Constrained Markov Model,” Journal of Agriculture Engineering Research, vol. 21, pages 281-289, 1976, suggested that the accumulation of sugar (percentage-wise) might be approximated as a quadratic function of time or age of the sugarcane.
Jiao, et al., in “An Integrated Statistical and Optimization Approach to Increasing Sugar Production Within a Mill Region,” Computers and Electronics in Agriculture, vol. 48, page 170-181, 2005 researched Australian sugarcane varieties (cultivars) and suggested that individual varieties (cultivars) have distinct sucrose maturation curves with different peak levels. This study concluded that the sugar content of a variety (cultivar) could be predicted as a function of time (i.e., age of the sugarcane at the time of harvest) with reasonable accuracy, and that the trend of sucrose accumulation within the same harvest season follows a second order curve.